Multilayer spunlaced nonwoven fire blocking composite

ABSTRACT

This invention relates to a mulilayer spunlaced nonwoven composite useful as a fire blocking component for an article, an article such as furniture or a mattress comprising the nonwoven composite, and processes for making the nonwoven composite and fire blocking an article with the nonwoven composite. The multilayer nonwoven composite comprises a first layer comprising 75 to 25 weight percent regenerated cellulosic fiber that retains at least 10 percent of its fiber weight when heated in air to 700° C. at a rate of 20 degrees C. per minute and 25 to 75 weight percent heat-resistant fiber, said first layer having a basis weight of from 1 to 5 ounces per square yard (34 to 170 grams per square meter); and a second layer comprising up to 75 weight percent of a regenerated cellulosic fiber that retains at least 10 percent of its fiber weight when heated in air to 700° C. at a rate of 20 degrees C. per minute, and 25 to 100 weight percent of a modacrylic fiber, said second layer having a basis weight of from 1 to 5 ounces per square yard (34 to 170 grams per square meter), the nonwoven composite having a total basis weight of from 2 to 7 ounces per square yard (68 to 237 grams per square meter).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a multilayer spunlaced nonwoven compositeuseful as a fire blocking component for an article, an article such asfurniture or a mattress or foundation comprising the nonwoven composite,and processes for making the nonwoven composite and fire blocking anarticle with the nonwoven composite.

2. Description of Related Art

The State of California has led the drive to regulate and reduce theflammability of mattresses and mattress sets in an attempt to reduce thenumber of lives lost in household, hotel, and institutional fires. Inparticular, the Bureau of Home Furnishings and Thermal Insulation of theDepartment of Consumer Affairs of the State of California issuedTechnical Bulletin 603 “Requirements and Test Procedure for Resistanceof a Residential Mattress/Box Spring Set to a Large Open-Flame” toquantify the flammability performance of mattress sets.

Mattresses normally contain a mattress core covered by cushioningmaterial or batting that is in turn covered with an outer fabricticking. Most cushioning material or batting is made from foam or fibermaterials that will burn when exposed to an open flame. One usefulmethod of fire blocking foam cushions, particularly airplane seats, isdisclosed in U.S. Pat. No. 4,750,443 to Blaustein, et al., wherein threeto seven layers of flame resistant fabrics are used underneath thecovering fabric of the seat to encase the foam. To the degree requiredper the aircraft seat flammability test method, these fire-blockedcushions withstand a flame jet impinging on the cushion and prevent theentire cushion from being engulfed by the flame or continuing to burnafter the flame jet is removed. When applied to mattresses, the use ofmultiple fire blocking layers underneath the ticking can add stiffnessor restrain the give of the mattress core, affecting overall comfort.

In addition, many fibers that are resistant to flame have a naturalcoloring based on their chemical structure. For example, fibers such aspara-aramid fibers are very useful in flame retardant fabrics and thesefibers have a natural gold color that is present in fabrics made fromsubstantial amounts of those fibers. However, it is undesirable for thenatural gold color of the para-aramid fabric to show through the outerticking of mattresses, which are normally of a white or light oroff-white color, or to show through the outer upholstery covering fabricof furniture. What is needed is a flexible fabric that incorporates aheat resistant fiber into a flame barrier wherein the color of that heatresistant fiber is masked by other fibers in the flame barrier, whichstill meeting important flame resistant requirements of the enduse.

PCT Publication WO 03/023108 discloses a nonwoven high loft flamebarrier for use in mattresses and upholstered furniture. These barriershave very low density, ranging from 5 to 50 kilograms per cubic meter,most preferably 7.5 kilograms per cubic meter. The preferred nonwovenhigh loft flame barrier comprises a blend of fibers including fibersthat are inherently fire resistant and resistant to shrinkage by directflame, and fibers from polymers made with halogenated monomers. Thesebarriers are designed to have bulk and cushioning, having as their majoruse as cushioning in the top and bottom panels of a mattress rather thanas a flexible, strong fabric that can be used in both the panels andborders in many different articles, including mattresses, foundations(such as box springs) and other furniture that either does not requirecushioning or where cushioning is provided by the use of veryinexpensive thermoplastic fiber batts and foams.

U.S. Pat. Nos. 6,132,476; 6,547,835, and 5,609,950 disclose fabricblends of inherently flame resistant fibers and cellulosic fibers havingincreased flame resistance; the fabric can contain an additional fireretardant that is added, for example, as an additive in a dyeing step.Because of the low content of inorganic material the flame resistantcellulose fiber disclosed in these references does not retain anadequate percentage of its weight when exposed to high temperatures.

U.S. Pat. No. 4,970,111 discloses a fire resistant non-woven fabric orfabric structure comprising a synergistic blend of about 35 to 80% byweight of chlorine-containing polymeric fibers, about 2 to 25% by weightof non-fusing fibers and about 10 to 55% by weight of a fire retardingpolyester binder. The non-fusing fibers preferably comprise fibersselected from the group consisting of oxidized polyacrylonitrile fibers,fiberglass, aramid (KEVLAR®, NOMEX®) and polybenzamidazole (PBI). Thesefabrics can be a single layer or multiple layers and are fusion bonded,requiring a binder to hold the structure together. The addition of abinder increases the chance the fabric will be “board-like” and haveunacceptable flexibility.

U.S. Pat. No. 6,596,658 discloses a flame resistant nonwoven fabriclaminate having a three-dimensional image formed therein by athree-dimensional image transfer device and treated with a fireretardant binder to stabilize the three-dimensional image and providethe laminate with flame retardant characteristics. The nonwoven fabriclaminate comprises a first layer formed of a dimensionally stable,heat-resistant entangled fibers such as NOMEX® fibers, the first layerhaving a basis weight of from about 1.0 to 3.0 ounces per square yard(34 to 102 grams per square meter), a second spunbonded support layerbonded by entanglement to the first layer, the second layer having abasis weight from about 2.0 to 5.0 ounces per square yard (68 to 170grams per square meter).

SUMMARY OF THE INVENTION

This invention relates to a multilayer nonwoven composite useful to fireblock articles, and a fire blocked article or mattress containing thecomposite. The multilayer nonwoven composite comprises a first layercomprising 75 to 25 weight percent regenerated cellulosic fiber thatretains at least 10 percent of its fiber weight when heated in air to700° C. at a rate of 20 degrees C. per minute and 25 to 75 weightpercent heat-resistant fiber, said first layer having a basis weight offrom 1 to 5 ounces per square yard (34 to 170 grams per square meter);and a second layer comprising up to 75 weight percent of a regeneratedcellulosic fiber that retains at least 10 percent of its fiber weightwhen heated in air to 700° C. at a rate of 20 degrees C. per minute, and25 to 100 weight percent of a modacrylic fiber, said second layer havinga basis weight of from 1 to 5 ounces per square yard (34 to 170 gramsper square meter), the nonwoven composite having a total basis weight offrom 2 to 7 ounces per square yard (68 to 237 grams per square meter).

This invention also relates to a method making a nonwoven compositeuseful in fire blocking, comprising the steps of:

-   -   a) combining a first layer and a second layer of staple fibers,        the first layer of staple fibers comprising 75 to 25 weight        percent regenerated cellulosic fiber that retains at least 10        percent of its fiber weight when heated in air to 700° C. at a        rate of 20 degrees C. per minute and 25 to 75 weight percent        heat-resistant fiber, and the second layer of staple fibers        comprising up to 75 weight percent regenerated cellulosic fiber        that retains at least 10 percent of its fiber weight when heated        in air to 700° C. at a rate of 20 degrees C. per minute and 25        to 100 weight percent modacrylic fiber; and    -   b) hydrolacing the first and second layers together to        consolidate the layers and form a unitary nonwoven composite.

This invention further relates to a method of fire blocking an article,comprising the steps of

-   -   a) combining a layer of nonwoven fire blocking composite, a        fabric ticking or upholstery layer, and optionally a cushioning        layer,    -   b) sewing the layers together to form a fire blocked quilt or        upholstery fabric, and    -   c) incorporating the fire blocked quilt or upholstery fabric        into the article,        -   the nonwoven fire blocking composite comprising a first            layer of staple fiber comprising 75 to 25 weight percent            regenerated cellulosic fiber that retains at least 10            percent of its fiber weight when heated in air to 700° C. at            a rate of 20 degrees C. per minute and 25 to 75 weight            percent heat-resistant fiber, said first layer having a            basis weight of from 1 to 5 ounces per square yard (34 to            170 grams per square meter); and a second layer of staple            fibers comprising up to 75 weight percent regenerated            cellulosic fiber that retains at least 10 percent of its            fiber weight when heated in air to 700° C. at a rate of 20            degrees C. per minute, and 25 to 100 weight percent            modacrylic fiber, said second layer having a basis weight of            from 1 to 5 ounces per square yard (34 to 170 grams per            square meter), the nonwoven composite having a total basis            weight of from 2 to 7 ounces per.square yard (68 to.237            grams per square meter).

The invention also relates to a multilayer nonwoven composite useful tofire block articles, comprising a first layer comprising regeneratedcellulosic fiber that retains at least 10 percent of its fiber weightwhen heated in air to 700° C. at a rate of 20 degrees C. per minute andheat resistant fiber, and a second layer comprising either regeneratedcellulosic fiber that retains at least 10 percent of its fiber weightwhen heated in air to 700° C. at a rate of 20 degrees C. per minuteand/or modacrylic fiber, the nonwoven composite having a total basisweight of from 2 to 7 ounces per square yard (68 to 237 grams per squaremeter) and a thickness of less than 75 mils, the multilayer nonwovencomposite providing adequate fire blocking to an article unable to passCalifornia Test Bulletin 603 to enable that article to pass CaliforniaTest Bulletin 603 without addition of a chemical flame retardantmaterial.

DETAILS OF THE INVENTION

This invention relates to a multilayer nonwoven composite useful to fireblock articles that not only performs in severe mattress burning testsbut is also thin and flexible so as to not detract from the comfort andfeel of typical mattresses. Such nonwoven composites preferably have atotal basis weight of from 2 to 7 ounces per square yard (68 to 237grams per square meter) and have a thickness in the range of about 15 to75 mils (0.4 to 1.9 mm). The composites preferably have two layers offibers made from two different intimate blends of staple fibers; the twolayers are superposed or laid one on the other and are consolidatedtogether, preferably by spunlacing with water jets, to form a unitarynon-patterned composite structure. The staple fibers used in thecomposite of this invention have cut lengths in the range of 0.4 to 2.5inches (1 to 6.3 cm) preferably 0.75 to 2 inches (1.9 to 5.1 cm).

The first layer of the nonwoven composite of this invention contains 75to 25 weight percent of a regenerated cellulosic fiber that retains atleast 10 percent of its fiber weight when heated in air to 700° C. at arate of 20 degrees C. per minute and 25 to 75 weight percent of aheat-resistant fiber. The intimate blend of two fibers work together toform a base layer for the multilayer nonwoven composite, the regeneratedcellulosic fiber generating a char layer when burned, while theheat-resistant fiber provides strength in flame to inhibit and/or reducethe break open of the layer.

The regenerated cellulose fibers used in the composite of this inventionpreferably have 10 percent inorganic compounds incorporated into thefibers and are said to be char forming. Such fibers; and methods formaking such fibers, are generally disclosed in U.S. Pat. No. 3,565,749and British Patent No. 1,064,271. A preferred char-forming cellulosefiber for this invention is a viscose fiber containing silicon dioxidein the form of a polysilicic acid with aluminum silicate sites. Suchfibers, and methods for making such fibers are generally disclosed inU.S. Pat. No. 5,417,752 and PCT Pat. Appl. WO 9217629. Viscose fibercontaining silicic acid and having approximately 31 (±3) percentinorganic material is sold under the trademark Visil® by Sateri OyCompany of Finland.

The other critical component in the first layer of the composite of thisinvention is heat resistant fiber. By “heat resistant” it is meant thatthe fiber preferably retains 90 percent of its fiber weight when heatedin air to 500° C. at a rate of 20 degrees C. per minute. Such fiber isnormally flame resistant, meaning the fiber or a fabric made from thefiber has a Limiting Oxygen Index (LOI) such that the fiber or fabricwill not support a flame in air, the preferred LOI range being greaterthan 26. The preferred fibers do not excessively shrink when exposed toa flame, that is, the length of the fiber will not significantly shortenwhen exposed to flame. Fabrics containing 0.5 ounces per square yard (17grams per square meter) of an organic fiber that retains 90 percent ofits fiber weight when heated in air to 500° C. at a rate of 20 degreesC. per minute tend to have limited amount of cracks and openings whenburned by an impinging flame, which is important to the fabricsperformance as a fire blocker.

Heat resistant and stable fibers useful in the nonwoven fire-blockingfabric of this invention include fiber made from para-aramid,polybenzazole, polybenzimidazole, and polyimide polymer. The preferredheat resistant fiber is made from aramid polymer, especially para-aramidpolymer.

As used herein, “aramid” is meant a polyamide wherein at least 85% ofthe amide (—CONH—) linkages are attached directly to two aromatic rings.Additives can be used with the aramid. In fact, it has been found thatup to as much as 10 percent, by weight, of other polymeric material canbe blended with the aramid or that copolymers can be used having as muchas 10 percent of other diamine substituted for the diamine of the aramidor as much as 10 percent of other diacid chloride substituted for thediacid chloride of the aramid. In the practice of this invention, thepreferred para-aramid is poly(paraphenylene terephthalamide). Methodsfor making para-aramid fibers useful in this invention are generallydisclosed in, for example, U.S. Pat. Nos. 3,869,430; 3,869,429; and3,767,756. Such aromatic polyamide organic fibers and various forms ofthese fibers are available from DuPont Company, Wilmington, Del. underthe trademark Kevlar® fibers.

Commercially available polybenzazole fibers useful in this inventioninclude Zylon® PBO-AS (Poly(p-phenylene-2,6-benzobisoxazole) fiber,Zylon® PBO-HM (Poly(p-phenylene-2,6-benzobisoxazole)) fiber, availablefrom Toyobo, Japan. Commercially available polybenzimidazole fibersuseful in this invention include PBI® fiber available from CelaneseAcetate LLC. Commercially available polyimide fibers useful in thisinvention include P-84® fiber available from LaPlace Chemical.

The first layer of the nonwoven composite of this invention contains 75to 25 weight percent of the regenerated cellulosic fiber and 25 to 75weight percent of the heat-resistant fiber, based on the total amount ofthese fibers in the layer. At least 25 weight percent of the heatresistant fiber is desired to achieve robust fire blocking performanceof the nonwoven composite. At least 25 weight percent of the regeneratedcellulosic fiber is desired to provide adequate char in the first layerof the nonwoven composite. The first layer preferably contains 55 to 45weight percent of the regenerated cellulosic fiber and 45 to 55 weightpercent of the heat-resistant fiber, based on the total amount of thesefibers in the layer.

The second layer of the nonwoven composite of this invention comprisesup to 75 weight percent of a regenerated cellulosic fiber that retainsat least 10 percent of its fiber weight when heated in air to 700° C. ata rate of 20 degrees C. per minute, and 25 to 100 weight percent of amodacrylic fiber. The fibers comprising the second layer are generallywhite or off-white and the second layer provides color shielding for thebase layer and provides additional char material to the nonwovencomposite if the regenerated cellulose is present.

Modacrylic fiber is used in the second layer of the nonwovenfire-blocking fabric composite of this invention because this fiberreleases flame-suppressing halogen-containing gases when burned. Bymodacrylic fiber it is meant acrylic synthetic fiber made from a polymercomprising primarily acrylonitrile. Preferably the polymer is acopolymer comprising 30 to 70 weight percent of an acrylonitrile and 70to 30 weight percent of a halogen-containing vinyl monomer. Thehalogen-containing vinyl monomer is at least one monomer selected, forexample, from vinyl chloride, vinylidene chloride, vinyl bromide,vinylidene bromide, etc. Examples of copolymerizable vinyl monomers areacrylic acid, methacrylic acid, salts or esters of such acids,acyrlamide, methylacrylamide, vinyl acetate, etc.

The preferred modacrylic fibers of this invention are copolymers ofacrylonitrile combined with vinylidene chloride, the copolymer having inaddition an antimony oxide or antimony oxides for improved fireretardancy. Such useful modacrylic fibers include, but are not limitedto, fibers disclosed in U.S. Pat. No. 3,193,602 having 2 weight percentantimony trioxide, fibers disclosed in U.S. Pat. No. 3,748,302 made withvarious antimony oxides that are present in an amount of at least 2weight percent and preferably not greater than 8 weight percent, andfibers disclosed in U.S. Pat. Nos. 5,208,105 and 5,506,042 having 8 to40 weight percent of an antimony compound.

The preferred modacrylic fiber is commercially available Protex C fromKaneka Corporation, Japan, which is said to contain 10 to 15 weightantimony oxides, although fibers having less antimony oxide, in therange of 6 weight percent or less, can also be used. The second layer ofthe nonwoven composite of this invention contains up to 75 weightpercent of a regenerated cellulosic fiber and 25 to 100 weight percentof a modacrylic fiber, based on the total amount of those fibers in thelayer. The regenerated cellulosic fiber provides the layer With charwhen the composite is burned, and at least 25 weight percent of themodacrylic fiber is needed to provide the desired flame-suppressingchlorine-containing gases, when the composite is burned. The secondlayer preferably contains 25 to 40 weight percent of the regeneratedcellulosic fiber and 75 to 60 weight percent of the modacrylic fiber,based on the total amount of those fibers in the layer.

Each of the first and second layers of the multilayer nonwoven compositeof this invention can have a basis weight ranging from 1 to 5 ounces persquare yard (34 to 170 grams per square meter) as long as the totalbasis weight of the composite is in the range of from 2 to 7 ounces persquare yard (68 to 237 grams per square meter). Preferably, each of thefirst and second layers of the multilayer nonwoven composite has a basisweight ranging from 1.25 to 2.5 ounces per square yard (42 to 85 gramsper square meter).

The multilayer nonwoven fabric composite of this invention is preferablya flexible fabric because of its intended use in articles such asmattresses and furniture. Stiff or “board-like” fabrics Would impartundesirable stiffness to such articles. The “hand” or flexibility of afabric composite in various directions can be measured using aHandle-O-Meter, resulting in a “Total Hand” measurement of the fabric.To insure the nonwoven fabric composites of this invention are flexiblethey preferably have a Total Hand measurement of less that 500grams-force.

The multilayer nonwoven fabric composite of this invention preferablyfunctions as a fire blocker without the addition of topical fireretardant chemical materials. It is believed the fire blockingperformance of such composites can be predicted by the fabriccomposite's performance in the Thermal Protective Performance (TPP)test. When measured, the multilayer nonwoven fabric composite of thisinvention preferably has a TPP rating greater than 9 calories per squarecentimeter.

The most preferred multilayer nonwoven composite of this invention has afirst layer that comprises 55 to 45 weight percent of a regeneratedcellulosic fiber containing silicic acid and 45 to 55 weight percent ofa poly(paraphenylene terephthalamide) fiber, and a second layer thatcomprises 25 to 40 weight percent of a regenerated cellulosic fibercontaining silicic acid and 75 to 60 weight percent of a modacrylicfiber.

The nonwoven composite of this invention can me made by combining afirst layer and a second layer of staple fibers, the first layer ofstaple fibers comprising 75 to 25 weight percent regenerated cellulosicfiber that retains at least 10 percent of its fiber weight when heatedin air to 700° C. at a rate of 20 degrees C. per minute and 25 to 75weight percent heat-resistant fiber, and the second layer of staplefibers comprising up to 75 weight percent regenerated cellulosic fiberthat retains at least 10 percent of its fiber weight when heated in airto 700° C. at a rate of 20 degrees C. per minute and 25 to 100 weightpercent modacrylic fiber; and then hydrolacing the first and secondlayers together to consolidate the layers and form a unitary nonwovencomposite.

The layers of the multilayer nonwoven composite of this invention can bemade by conventional nonwoven sheet forming processes utilizing staplefibers, including processes for making carded webs, air-laid webs,and/or wet-laid webs. Preferably, the first and second layers are madeby forming fiber webs using separate carding machines and laying firstone web on a moving wire belt and then laying the second web on thefirst web to form the first and second unconsolidated layers having thecompositions as described herein. Such formed webs are preferablyconsolidated into useable fabrics via processes commonly known asspunlacing or hydrolacing where high-pressure fluid jets are used toentangle the staple fibers into a useable fabric, however otherprocesses that can generate a nonwoven sheet may be used. Theweb-formation and spunlacing processes disclosed in U.S. Pat. Nos.3,508,308; 3,493,462; 3,403,862; and 3,797,074 are examples of methodswell-known in the art that are useful in the manufacture of the nonwovenfabric of this invention. The preferred nonwoven fabrics of thisinvention are made from carded webs of cut staple fibers that utilizepressurized water jets to entangle the fibers and consolidate the layersinto a non-patterned cohesive sheet.

This invention further relates to a method of fire blocking an article,comprising the steps of (1) combining a layer of nonwoven fire blockingcomposite, a fabric ticking or upholstery layer, and optionally acushioning layer; (2) sewing the layers together to form a fire blockedquilt or upholstery fabric, and (3) incorporating the fire blocked quiltor upholstery fabric into the article. The nonwoven fire blockingcomposite comprises a first layer of staple fiber comprising 75 to 25weight percent regenerated cellulosic fiber that retains at least 10percent of its fiber weight when heated in air to 700° C. at a rate of20 degrees C. per minute and 25 to 75 weight percent heat-resistantfiber, and a second layer of staple fibers comprising up to 75 weightpercent regenerated cellulosic fiber that retains at least 10 percent ofIts fiber weight when heated In air to 700° C. at a rate of 20 degreesC. per minute, and 25 to 100 weight percent modacrylic fiber. Both firstand second layers have a basis weight of from 1 to 5 ounces per squareyard (34 to 170 grams per square meter), and the total nonwovencomposite has a basis weight of from 2 to 7 ounces per square yard (68to 237 grams per square meter).

Preferably, the multilayer nonwoven composite of this invention ispositioned in the article such that the second layer of the nonwovencomposite, which is preferably white, offwhite, or light in color iscloser to or faces the exterior of the article, and the first layer ofthe nonwoven is closer to or faces the interior of the article. In otherwords, the multilayer nonwoven composite is preferably positioned in thearticle such that the second layer visually masks the color of the firstlayer.

The combination of nonwoven fire blocking composite, fabric ticking orupholstery layer, and optionally a cushioning layer, are sewn orstitched together to form a pre-stitched quilt and these quilts can havemany forms. A basic example of a quilt comprises, in order, an outerfabric ticking or cover fabric layer, one or more layers of themultilayer nonwoven composite fire blocker of this invention, acushioning layer of foam or fiber batting, and a stitch-backing layer.The layers are combined and then stitched together using any commonstitch pattern, typically a quilting pattern, to form a quilt that isused in the mattress borders and panels as needed.

Fabrics useful as the outer fabric ticking or cover fabric layer arenormally very durable woven or knit fabrics utilizing any number ofweaves, and tend to have basis weights in the range of 2 to 8 ounces persquare yard (68 to 271 grams per square meter). Ticking fabrics maycontain but are not limited to cotton, polyester fibers, polypropylenefibers, or rayon fibers.

The optional cushioning layer of foam or fiber batting may include oneor more light density fibrous batting or foams, or a combination thereofthat provides the desired surface effect or cushion. The batting and/orfoams acts like a pillow underneath the ticking, providing very tactilecushioning, the type that can be readily discerned by simply touching orrunning one's hand across the mattress. The preferred fibrous battingmaterial is polyester (PET) batting and is typically present in anamount of about 0.5 to 2.0 ounces per square foot (153 to 610grams/square meter). While not intended to be limiting, if thecushioning material is a fibrous batting, such batting may include avertically pleated structure such as disclosed in, for example, in PCTPublication WO 2003049581 or a batting of fibers such as disclosed forexample in U.S. Pat. No. 3,118,750. If foam is used, it is commonlypolyurethane or latex foam and is typically 0.5 to 3 inches (1.2 to 7.6cm) thick.

The stitch-backing layer is typically used to hold the stitch on theside of the quilt opposite the ticking when the cushioning material isnot substantial enough to hold a stitch. Typically, stitch-backinglayers are lightweight fabrics having a basis weight in the range of 0.5ounces per square yard (17 grams per square meter) and are made frommaterials such as polypropylene.

An alternative quilt layer configuration can be, in order, an outerticking or upholstery layer, a layer of cushioning material, and one ormore layers of the multilayer nonwoven composite fire blocker, whereinthe cushioning material is sandwiched between the fire blocker and theticking. In this quilt, no stitch backing is needed because the fireblocker serves the purpose of holding the stitch. Another version of thequilt can be made with multiple layers of cushioning material. Forexample, a quilt can be formed by combining, in order, outer ticking orupholstery fabric, a layer of cushioning material, one or more layers ofthe multilayer nonwoven composite fire blocker, another layer ofcushioning material, and then a stitch-backing layer.

Another possible quilt configuration is one in which one layer of themultilayer nonwoven composite fire blocker of this invention is placeddirectly under the outer cover fabric, followed, by a cushioning layer,with a second layer of the multilayer nonwoven composite fire blockerunder the cushioning layer. In this configuration the last layer of themultilayer nonwoven composite fire blocker also functions as a stitchbacking. In an alternative version of this particular quiltconfiguration, another layer of cushioning can be disposed between thecover fabric and the multilayer nonwoven composite fire blocker.

Still another quilt configuration could be comprised of an outer tickingor upholstery layer and one or more layers of the multilayer nonwovencomposite fire blocker of this invention, with no substantial cushioninglayer. As one can see, many different quilts are possible and otherlayers of materials can be combined in the quilts as long as thefire-blocking performance of the quilt is not adversely affected.

The pre-stitched quilts may then be incorporated into an article such asa piece of furniture, or preferably, a mattress and foundation set. Onemethod of fire blocking the mattress is by fully covering the panels andborders of the mattress core with the pre-stitched quilts, and sewingthe quilts together at the seams to encapsulate the mattress. Thisinsures the mattress will be fire blocked regardless of which panel orborder is exposed to the flame. Pre-stitched quilts of various types canbe incorporated into an article, such as a quilt having littlecushioning can be used in the border of a mattress while a quilt havinga considerable amount of cushioning can be used in the top and bottompanels of the same mattress. Foundations, such as box springs, do notnormally have to be completely fire blocked but generally are onlyrequired to have fire blocking on the borders with fire blocking beingoptional for the top face or panel of the foundation. This foundationpanel is normally in contact with the mattress and is thus generallyshielded from flame so the material used in the foundation panel doesnot typically have to have the same degree of fire blocking as the panelof the mattress. Further, the mattress foundation may not have a largedegree of cushioning material in the border and/or the panel. However,the multilayer nonwoven composite of this invention can be used ineither the foundation border or panel as desired.

The invention also relates to a multilayer nonwoven composite useful tofire block articles, and an article comprising the composite, themultilayer nonwoven composite comprising a first layer comprisingregenerated cellulosic fiber that retains at least 10 percent of itsfiber weight when heated in air to 700° C. at a rate of 20 degrees C.per minute and heat-resistant fiber, and a second layer comprisingeither regenerated cellulosic fiber that retains at least 10 percent ofits fiber weight when heated in air to 700° C. at a rate of 20 degreesC. per minute or modacrylic fiber, the nonwoven composite having a totalbasis weight of from. 2 to 7 ounces per square yard (68 to 237 grams.per square meter) and a thickness of less than 75 mils (1.9 mm), themultilayer nonwoven composite providing adequate fire blocking to anarticle unable to pass California Technical Bulletin 603 issued July2003, to enable that article to pass California Technical Bulletin 603issued July 2003 without addition of a chemical flame retardantmaterial. The multilayer nonwoven composite can be incorporated into thearticle, such as a mattress, in any manner that allows that mattress topast the test when it would otherwise not pass.

Test Methods

Mattress Burn Performance

The Bureau of Home Furnishings and Thermal Insulation of the Departmentof Consumer Affairs of the State of California (3485 Orange GroveAvenue, North Highlands, Calif. 95660-5595, USA) published TechnicalBulletin 603 “Requirements and Test Procedure for Resistance of aResidential Mattress/Box Spring Set to a Large Open-Flame” datedFebruary 2003 to quantify the flammability performance of mattress sets.The bulletin was later revised in July 2003, requiring the limit of PeakHeat Release Rate (PHRR) to be less than 200 kilowatts and the TotalHeat release limit at 10 minutes to be less than 25 megajoules. Thisprotocol provides a means of determining the burning behavior ofmattress/foundation sets by measuring specific fire test responses whenthe mattress plus foundation are exposed to a specified flaming ignitionsource under well-ventilated conditions. It is based on the NationalInstitute of Standards and Technology Publication titled “Protocol ofTesting Mattress/Foundation Sets Using a Pair of Gas Burners” datedFebruary 2003.

Test data are obtained that describe the burning during and subsequentto the application of a specific pair of gas burners from the point ofignition until (1) all burning of the sleep set has stopped, (2) aperiod of 30 minutes has elapsed, or (3) flashover of the test roomappears inevitable. The rate of heat release from the burning testspecimen (the energy generated by the fire) is measured by oxygenconsumption calorimetry. A discussion of the principles, limitations,and requisite instrumentation are found in ASTM E 1590 “Standard TestMethod of Fire Testing of Mattresses”. Terminology associated with thetesting is defined in ASTM E 176 “Standard Terminology of FireStandards”.

In general, the test protocol utilizes a pair of propane burners,designed to mimic the heat flux levels and durations imposed on amattress and foundation by burning bedclothes. The burners imposediffering fluxes for differing times on the mattress top and the side ofthe mattress/foundation. During and subsequent to this exposure,measurements are made of the time-dependent heat release rate from thetest specimen.

The mattress/foundation is placed on top of a short bed frame that sitson a catch surface. During the testing, the smoke plume is caught by ahood that is instrumented to measure heat release rate. Forpracticality, twin-sized mattresses and foundations are tested. Afterignition by the burners, the specimen is allowed to burn freely underwell-ventilated conditions.

The test specimen includes a mattress that is placed on foundation withT-shaped burners set to burn the specimen. One burner impinges flames onthe top surface of the mattress and is set 39 mm from the surface of themattress. The second burner impinges flames vertically on the side ofthe mattress/foundation combination and is set 42 mm from the side ofthe specimen. The side burner and the top burner are not set at the sameplace along the length of the specimen but are offset from on anotheralong the length approximately 18 to 20 cm. The burners are speciallyconstructed and aligned per the test method.

The test specimen is conditioned for 24 hours prior to the testing at anambient temperature of above 12 Celsius (54 Fahrenheit) and a relativehumidity of less than 70 percent. The test specimen of mattress andfoundation is centered on each other and the frame and catch surface. Ifthe mattress is 1 to 2 cm narrower than the foundation the mattress maybe shifted until the sides of the mattress and foundation are alignedvertically. The burners are aligned and spaced from the specimen per thestandard. Data recording and logging devices are turned on at least oneminute prior to ignition. The burners are ignited and the top burner isallowed to burn for 70 seconds while the side burner is allowed to burnfor 50 seconds (if possible) and then they are removed from the area.Data collection continues until all signs of burning and smoldering haveceased or until one hour has elapsed.

ThermoGravametric Analysis

The fibers used in this invention retain a portion of their fiber weightwhen heated to high temperature at a specific heating rate. This fiberweight was measured using a Model 2950 Thermogravimetric Analyzer (TGA)available from TA Instruments (a division of Waters Corporation) ofNewark, Del. The TGA gives a scan of sample weight loss versusincreasing temperature. Using the TA Universal Analysis program, percentweight loss can be measured at any recorded temperature. The programprofile consists of equilibrating the sample at 50 degrees C.; rampingthe temperature at from 10 or 20 degrees C. per minute from 50 to 1000degrees C.; using air as the gas, supplied at 10 ml/minute, and using a500 microliter ceramic cup (PN 952018.910) sample container.

The testing procedure is as follows. The TGA was programmed using theTGA screen on the TA Systems 2900 Controller. The sample ID was enteredand the planned temperature ramp program of 20 degrees per minuteselected. The empty sample cup was tared using the tare function of theinstrument. The fiber sample was cut into approximately 1/16″ (0.16 cm)lengths and the sample pan was loosely filled with the sample. Thesample weight should be in the range of 10 to 50 mg. The TGA has abalance therefore the exact weight does not have to be determinedbeforehand. None of the sample should be outside the pan. The filledsample pan was loaded onto the balance wire making sure the thermocoupleis close to the top edge of the pan but not touching it. The furnace israised over the pan and the TGA is started. Once the program iscomplete, the TGA will automatically lower the furnace, remove thesample pan, and go into a cool down mode. The TA Systems 2900 UniversalAnalysis program is then used to analyze and produce the TGA scan forpercent weight loss over the range of temperatures.

Thermal Protective Performance Test (TPP)

The predicted protective performance of the multilayer nonwovencomposite of this invention in heat and flame was measured using the“Thermal Protective Performance Test” NFPA 2112. A combined radiant andconvective heat source is directed at a section of nonwoven composite(the test specimen) mounted in a horizontal position at a specified heatflux (typically 2 cal/cm²/sec). The test measures the transmitted heatenergy from the source through the specimen using a copper slugcalorimeter with no space between the fabric and heat source. The testendpoint is characterized by the time required to attain a predictedsecond-degree skin burn injury using a simplified model developed byStoll & Chianta, “Transactions New York Academy Science”, 1971, 33 p649. The value assigned to a specimen in this test, denoted as the TPPvalue, computed by multiplying the imposed heat flux times the testend-point time is the total heat energy that the specimen can withstandbefore a second degree burn is expected. Higher TPP values denote betterinsulation performance.

Total Hand

The Total Hand of each barrier was measured using INDA Standard Test IST90.3(01); Standard Test Method for Handle-O-Meter Stiffness of NonwovenFabrics. The INDA standard utilizes the Handle-O-Meter apparatus tomeasure the force required to flex a nonwoven fabric sample into but notthrough a fixed width slot. This force is measured in the machine andcross directions on both sides of the fabric resulting in four forcemeasurements. These four force measurements are then combined to theresulting Total Hand reported in force units.

Thickness

Thickness results were based on ASTM D1777-96, Standard Test Method forThickness of Textile Materials.

EXAMPLE 1

A multilayered spunlaced nonwoven fabric composite was prepared asfollows. Two staple fiber blends were made from bales on 2 separatelyfed lines from 3 different fibers as follows. Blend A was 50/50 blend ofType 970 2.2 denier per filament (dpf) (2.4 dtex/filament) Kevlar® brandstaple fiber having a 2″ (5 cm) cut length and Type 33AP 1.5 dpf (1.7dtex/filament) Visil® brand staple fiber having a 1.6″ (4.1 cm) cutlength. Blend B was a 67/33 blend of 1.5 dpf (1.7 dtex/filament) ProtexC brand modacrylic staple fibers having a 1.6″ (4.1 cm) cut length andType 33AP 1.5 dpf (1.7 dtex/filament) Visil® brand staple fiber having a1.6″ (4.1 cm) cut length.

One opening and carding line prepared Blend A and laid a 2.5 oz./sq.yd.(85 grams/sq. meter) 96″ (244 cm) wide web of the blend on a transferbelt creating Web A. At the same time, a second opening and carding lineprepared Blend B and laid a 4.0 oz./sq. yd. (136 grams/sq. meter), 91″(231 cm) wide web of Blend B on top of Web A and both were carried onthe belt into a Perfojet hydro-entangling machine. The webs wereconsolidated with hydrolacing water jets and a cohesive two-layernonwoven composite was formed having a total basis weight of 6.5 ouncesper square yard (220 grams per square meter) and a total handmeasurement of 490 grams force. The nonwoven composite also had a TPPrating of 21 calories per square centimeter and a total thickness of 67mils (1.7 mm).

This composite was then incorporated as a barrier layer in a double sidetight mattress. A panel quilt for the top and bottom panels of themattress was made by combining, in order, mosaic stylepolyester/polypropylene white woven ticking fabric; ¾″ (1.9 cm)polyester batting; the two-layered nonwoven composite made above; 3layers of 7/16″ (1.1 cm) polyurethane foam; and polystitch backingfabric; the layers were then stitched together with non-FR thread.

A border quilt for the border of the mattress was made by combining, inorder, mosaic style polyester/polypropylene white woven ticking fabric;the two-layered nonwoven composite made above; 3/16″ (0.48 cm)polyurethane foam; and polystitch backing fabric; the layers were thenstitched together with non-FR thread.

The mattress was then constructed having as internals gray feltinsulator pad against 522 Highpro mattress springs; the gray feltinsulator pad was then covered, in order, by 7/16″ (1.1 cm) polyurethanefoam and 1-½″ (3.8 cm) convoluted polyurethane foam. The top and bottomof the mattress were then covered with the panel quilt and the borderswere covered with the border quilt, with the seams sewn with FRpolyester tapes and fire-resistant aramid thread.

The foundation was a box spring having the same border quilt as used forthe mattress and having as a top panel a non-skid pad comprised of alightweight polyester-type fabric. The foundation was assembled from awooden frame with a stiff cardboard layer stapled to the frame, thecardboard forming the support for the top panel of the foundation. A 4oz./sq. yard (136 grams/sq. meter) spunlaced fabric containing 25%Kevlar®/75% Visil® 33AP fiber was then stapled to the frame over thecardboard, overlapping the top edges and extending down the sides of theframe approximately 1 inch (2.5 cm). The border quilt and non-skid padwere sewn together with FR polyester tapes and fire-resistant aramidthread such that the side borders were long: enough to overlap the toppanel 2 inches (5 cm) in what is called a continental border. Thequiltnon-skid pad combination was then slid over and secured to theframe with staples.

The mattress and foundation was burned as described in CaliforniaTechnical bulletin TB-603 as revised July 2003. The mattress easilypassed the Peak Heat Release Rate limit (<200 KW) with a PHRR of <50 KWand the Total Heat release limit at 10 min. (<25 MJ) with a value of <10MJ.

EXAMPLE 2

Multilayered spunlaced nonwoven fabric composites of various weightswere made as in Example 1, having a 50/50 blend of Kevlar®/Visil® in thefirst layer and a 33/67 blend of Visil®/Modacrylic in the second layer.The composites were tested to determine their TPP. rating, Total Handmeasurement, and TB603 (as revised July 2003) Burn, Test Results, whichare summarized in the Table (data for the nonwoven composite of Example1 is also included). TB603 Burn Tests were run on both single-sided anddouble-sided tight top mattresses. A number of mattresses were made andtested, all of which passed the TB603. (as revised July 2003) burn test.TABLE Nominal Basis Weight Burn Test oz/yd² (g/m²) Total Total TPPSingle Double 1st 2^(nd) Thickness Hand Rating Density Sided Sided LayerLayer Total (mil)(mm) (gf) cal/cm² g/cc² (No. Passed) 1.25(42) 1.25(42)  2.5(85)  24 (0.6)  69 10 0.1 6 of 6 6 of 6 1.9(64) 1.9(64)3.8(129) 39 (1.0) 286 12 0.1 3 of 3 3 of 3 2.25(76)  2.25(76)  4.5(153)49 (1.2) 319 15 0.1 3 of 3 3 of 3 2.5(85) 2.5(85) 5.0(170) 63 (1.6) 31618 0.1 2 of 2 —*— 2.5(85)  4.0(135) 6.5(220) 67 (1.7) 490 21 0.1 2 of 22 of 2*Mattress Not Made or Tested

1-11. (canceled)
 12. A method making a nonwoven composite useful in fireblocking, comprising the steps of a) combining a first layer and asecond layer of staple fibers, the first layer of staple fiberscomprising 75 to 25 weight percent regenerated cellulosic fiber thatretains at least 10 percent of its fiber weight when heated in air to700° C. at a rate of 20 degrees C. per minute and 25 to 75 weightpercent heat-resistant fiber, and the second layer of staple fiberscomprising up to 75 weight percent regenerated cellulosic fiber thatretains at least 10 percent of its fiber weight when heated in air to700° C. at a rate of 20 degrees C. per minute and 25 to 100 weightpercent modacrylic fiber; and b) hydrolacing the first and second layerstogether to consolidate the layers and form a unitary nonwovencomposite.
 13. The method of making a nonwoven composite of claim 12,wherein the first layer of staple fibers is superposed over the secondlayer of staple fibers prior to hydrolacing.
 14. The method of making anonwoven composite of claim 12, wherein the first and second layers areconsolidated by hydrolacing such that the total hand measurement of thenonwoven composite is less than 500 grams force.
 15. The method ofmaking a nonwoven composite of claim 12, wherein the first layer ofstaple fibers has a basis weight of 1 to 5 ounces per square yard (34 to170 grams per square meter).
 16. The method of making a nonwovencomposite of claim 12, wherein the second layer of staple fibers has abasis weight of 1 to 5 ounces per square yard (34 to 170 grams persquare meter).
 17. A method of fire blocking an article, comprising thesteps of a) combining a layer of nonwoven fire blocking composite, afabric ticking or upholstery layer, and optionally a cushioning layer,b) sewing the layers together to form a fire blocked quilt or upholsteryfabric, and c) incorporating the fire blocked quilt or upholstery fabricinto the article, the nonwoven fire blocking composite comprising afirst layer of staple fibers comprising 75 to 25 weight percentregenerated cellulosic fiber that retains at least 10 percent of itsfiber weight when heated in air to 700° C. at a rate of 20 degrees C.per minute and 25 to 75 weight percent heat-resistant fiber, said firstlayer having a basis weight of from 1 to 5 ounces per square yard (34 to170 grams per square meter); and a second layer of staple fiberscomprising up to 75 weight percent regenerated cellulosic fiber thatretains at least 10 percent of its fiber weight when heated in air to700° C. at a rate of 20 degrees C. per minute, and 25 to 100 weightpercent modacrylic fiber, said second layer having a basis weight offrom 1 to 5 ounces per square yard (34 to 170 grams per square meter);the nonwoven composite having a total basis weight of from 2 to 7 ouncesper square yard (68 to 237 grams per square meter).
 18. The method offire blocking an article of claim 17, wherein the heat-resistant fiberis a para-aramid fiber.
 19. The method of fire blocking an article ofclaim 17, wherein first layer comprises 55 to 45 weight percentregenerated cellulosic fiber containing silicic acid and 45 to 55 weightpercent poly(paraphenylene terephthalamide) fiber, and second layercomprises 25 to 40 weight percent regenerated cellulosic fibercontaining silicic acid and 75 to 60 weight percent modacrylic fiber.20. The method of fire blocking an article of claim 17, wherein theregenerated cellulosic fiber contains silicic acid. 21-24. (canceled)